please don't use the Skype property for control of resolutions at all. Skype will select other resolutions by using testing your Inet channel.
For example, at start Skype connects to Splitcam and asks it to set the resolution: 640x360. Splitcam will do it. If your channel passes it,
then Skype asks Splitcam to change that resolution on 1280x720 and etc. You can see as a Skype changes these video parameters using the Menu command: Call->Call Tech. Info.

So if you wish to have a good resolution, set it in Splitcam. In this case, Splicam sets this original resolution on the webcam and offers it to Skype.
If Skype doesn't like that resolution, it asks Splitcam to change it using the following schema:

Sorry, but we don't speak about original quality, their original resolutions.
Our question was about the Splitcam output resolutions. Splitcam creates them from the original resolution by Skype request .
For their creating Splitcam uses interpolation methods. Hence, their quality is lower than for original.

So my question - why do you need that resolution 720x576, if Skype will not use it?